A known roof apparatus used for a sun roof or the like, which opens and closes an opening provided at a roof, includes a frame extending in a width direction of a vehicle for securing vehicle strength required at a time of lateral collision.
This kind of roof apparatus includes a movable panel for opening and closing the opening and guide rails for guiding the movable panel. The guide rails extend in a longitudinal direction of the vehicle at left and right sides of the opening and are connected with each other by a frame. The frame is made of steel plates and the guide rails are made of an aluminum alloy. The frame and each guide rail are joined at recessed joining portions which fit into each other. The frame and the guide rail are joined by TOX® caulking which forms the joining portions in one process. Since material rigidity is different between the steel and the aluminum alloy, the frame includes a thin steel plate for interlocking the frame and each guide rail to be properly joined by TOX® caulking. Further, the frame includes a thick steel plate for securing necessary strength against a load of lateral collision, and the thin steel plate and thick steel plate are welded. For example, refer to JP 2006-327250A.
However, the frame of the roof apparatus shown in JP 2006327250 is formed by the two steel plates, thus increasing the weight. Further, welding is required, and the cost increases for welding. Furthermore, the cross sectional shape of the frame, formed by folding the steel plates, tends to bend easily by the load due to the lateral collision, which is applied to the frame in a length direction thereof. In other words, the frame is not likely to deform stably.
A need exists for a roof apparatus which is not susceptible to the drawback mentioned above.